A rotary pre-heater for high temperature operation

ABSTRACT

A rotary pre-heater having a cold-end rotor and a hot-end rotor including an insulation assembly including a plurality of elongate retainer elements. Each of the retainer elements has a root end adapted to be held in fixed relationship to the cold-end rotor and a distal end proximate to the hot-end rotor. Portions of each of the plurality of retainer elements are adapted for circumferential movement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of and claims priority to PCT Application No. PCT/US2017/026187, entitled “INSULATION RETAINING ASSEMBLY FOR A ROTARY PRE-HEATER FOR HIGH TEMPERATURE OPERATION,” filed Apr. 5, 2017, which is a PCT Application of and claims priority to U.S. patent application Ser. No. 15/091,200, entitled “ROTARY PRE-HEATER FOR HIGH TEMPERATURE OPERATION,” filed Apr. 5, 2016, the subject matter of both aforementioned applications are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to a rotary pre-heater for high temperature operation, and more particularly to an insulation retaining assembly for a rotor of a rotary pre-heater, which can withstand high temperature operation.

BACKGROUND OF THE INVENTION

Rotary regenerative heat exchangers or pre-heaters are commonly used to recover heat from various combustion and chemical reaction processes, including those associated with the production of synthesis gas (also referred to as Syngas). Conventional rotary regenerative heat exchangers have a rotor mounted in a housing that defines an inlet duct and an outlet duct for the flow of heated flue gases through the heat exchanger. The housing further defines another set of inlet ducts and outlet ducts for the flow of gas streams that receive the recovered heat energy. The rotor has radial partitions or diaphragms defining compartments therebetween for supporting baskets or frames to hold heat transfer sheets. Typically, the rotor and baskets are manufactured from metallic materials.

However, in very high temperature applications (e.g., temperatures exceeding 2100 degrees Fahrenheit (1149 degrees Celsius)), for example in Syngas production systems, typical rotary regenerative heat exchangers have insufficient strength and oxidation can occur on the surfaces thereof. As a result, typical rotary regenerative heat exchangers can fail to operate at such high temperatures.

Thus, there is a need for an improved rotary pre-heater that can withstand high temperature operation.

SUMMARY

There is disclosed herein an insulation retaining assembly for a high temperature rotary pre-heater having a cold-end rotor and a hot-end rotor. The insulation retaining assembly includes a plurality of elongate retainer elements. Each of the retainer elements has a root end adapted to be held in fixed relationship to the cold-end rotor and a distal end proximate to the hot-end rotor. Portions of each of the plurality of retainer elements are adapted for circumferential movement.

In one embodiment, each of the plurality of retainer elements has a first connection area at the root end and a second connection area at the distal end. The insulation retaining assembly includes a plurality of groups of retainer elements. Each of the plurality of groups includes two or more of the retainer elements. Adjacent retainer elements in each of the groups are secured to one another at the first connection area and the second connection area. Adjacent groups are secured to one another at the first connection area, thereby forming a closed loop about a central axis to preclude circumferential movement of adjacent groups of retainer elements relative to one another or relative to the cold-end rotor. Adjacent groups are separate from one another outside of the first connection area so that each of the groups is moveable in a circumferential direction about the central axis.

In one embodiment, each of the plurality of the retainer elements has an L-shaped configuration defining a first leg and a second leg. The second leg is shorter than the first leg and extends radially inward from the first leg.

In one embodiment, the first connection area is positioned on a first end of the first leg and the second connection area is positioned on a second end of the second leg.

There is also disclosed herein another rotary pre-heater. The rotary pre-heater includes an annular housing, a hot-end connecting plate, a cold-end connecting plate and a rotor. The hot-end connecting plate has a first inlet and a first outlet and is secured to a first axial end of the annular housing. The cold-end connecting plate has a second inlet and a second outlet and is secured to a second axial end of the annular housing. The rotor is disposed for rotation in the annular housing between the hot-end connecting plate and the cold-end connecting plate. The rotor includes a cold-end rotor mounted for rotation on a spindle proximate the cold-end connecting plate. The cold-end rotor has a first plurality of flow passages extending therethrough. The rotor includes a hot-end rotor assembly disposed on the cold-end rotor. The hot-end rotor assembly is proximate the hot-end connecting plate, the hot-end rotor assembly has a second plurality of flow passages extending therethrough. The rotor includes an insulation assembly surrounding an exterior surface defined by the annular rim.

The insulation retaining assembly includes a plurality of elongate retainer elements. Each of the retainer elements has a root end adapted to be held in fixed relationship (e.g., no or essentially no circumferential movement of the root end) to the cold-end rotor and a distal end proximate to the hot-end rotor. Portions of each of plurality of retainer elements are adapted for circumferential movement.

In one embodiment, each of the plurality of retainer elements has a first connection area at the root end and a second connection area at the distal end. The insulation retaining assembly includes a plurality of groups of retainer elements. Each of the plurality of groups includes two or more of the retainer elements. Adjacent retainer elements in each of the groups are secured to one another at the first connection area and the second connection area. Adjacent groups are secured to one another at the first connection area, thereby forming a closed loop about a central axis to preclude circumferential movement of adjacent groups of groups of retainer elements relative to one another or relative to the cold-end rotor. Adjacent groups are separate from one another outside of the first connection area so that each of the groups is moveable in a circumferential direction about the central axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of the rotary pre-heater of the present invention;

FIG. 2 a top cross sectional view of the rotary pre-heater of FIG. 1 taken across line 2-2;

FIG. 3 is an enlarged view if a portion of the rotary pre-heater of FIG. 2;

FIG. 4 is a perspective view of the cold-side connecting plate taken across line 4-4 of FIG. 1;

FIG. 5 is a perspective view of the cold-end rotor mounted on the cold side connecting plate taken across line 5-5 of FIG. 1;

FIG. 6 is a schematic drawing of a ceramic heat transfer media section for installation in the hot-side rotor of FIG. 3;

FIG. 7 is an enlarged view of a portion of the ceramic heat transfer media section of FIG. 6;

FIG. 8 is a perspective view of a ceramic rotor portion of the rotary pre-heater of FIG. 1;

FIG. 9 is an enlarged view of detail A of FIG. 1;

FIG. 10 is a detailed cross sectional view of a portion of two groups retainer elements;

FIG. 11 is an enlarged view of a portion of the ceramic rotor portion of detail B of FIG. 3

FIG. 12 is an enlarged view of a portion of another embodiment of the ceramic rotor portion of detail B of FIG. 3 and

FIG. 13 is an enlarged view of a portion of yet another embodiment of the ceramic rotor portion of detail B of FIG. 3

DETAILED DESCRIPTION

As shown in FIG. 1, a rotary pre-heater for high temperature operation is generally designated by the numeral 10. The rotary pre-heater 10 is suitable for use in the production of Syngas, or synthesis gas, which is a fuel gas mixture consisting primarily of hydrogen, carbon monoxide, and some carbon dioxide. The rotary pre-heater 10 has a generally annular housing 12 that extends between a hot-end flange 12A formed at a first axial end 12X of the annular housing 12 and a cold-end flange 12B formed at a second axial end 12Y of the annular housing 12. The annular housing 12 is lined with a suitable refractory 12R (e.g., a ceramic based refractory) wrapped in a ceramic fiber blanket 12Q providing thermal insulation between the refractory 12R and housing 12.

As shown in FIG. 1, the rotary pre-heater 10 includes a hot-end connecting plate 14 having a first inlet 14A defined by a flange 14F and a first outlet 14B defined by a flange 14G. The hot-end connecting plate 14 is associated with a hot side of the rotary pre-heater 10 into which hot gases (e.g., 2100 degrees Fahrenheit (1149 degrees Celsius and higher)) depleted in oxygen flow via the first inlet 14A. The hot-end connecting plate 14 has a flange 14H formed on an axial end thereof, opposite the first inlet 14A and the first outlet 14B. The flange 14H of the hot-end connecting plate 14 is secured to the hot-end flange 12A of the annular housing 12 via suitable fasteners (not shown).

As shown in FIGS. 1 and 4, the rotary pre-heater 10 includes a cold-end connecting plate 16 having a second inlet 16A defined by a flange 16F and a second outlet 16B defined by a flange 16G. The cold-end connecting plate 16 is associated with a cold side of the rotary pre-heater 10 into which cold air to be heated flows via the second inlet 16A. The cold-end connecting plate 16 has a flange 16H formed on an axial end thereof, opposite the second inlet 16A and the second outlet 16B. The flange 16H of the cold-end connecting plate 16 is secured to the flange 12B of the annular housing 12 and a flange 18H of a frame 18 via suitable fasteners (not shown). As shown in FIG. 4, the second inlet 16A of the cold-end connecting plate 16 is an arcuate segment; and the second outlet 16B is another arcuate segment. The arcuate segments define the second inlet 16A and the second outlet 16B which are separated from one another by a flat plate segment 17. The cold-end connecting plate 16 has a centrally located bore 16R extending therethrough for receiving a spindle 25 as described further herein with reference to FIG. 1.

As shown in FIG. 1, a rotor 20 is disposed for rotation in the refractory lined annular housing 12 and axially between the hot-end connecting plate 14 and the cold-end connecting plate 16. The rotor 20 includes a cold-end rotor 22 mounted for rotation on the spindle 25 proximate the cold-end connecting plate 16. The spindle 25 is supported by a suitable bearing 19 (e.g., a tapered thrust bearing). A motor 29 is coupled to a gearbox 29G that is coupled to the spindle 25 for rotation of the rotor 20 relative to the annular housing 12.

As shown in FIGS. 1 and 5, the cold-end rotor 22 has a plurality of first flow passages 22P extending therethrough. Each of the first flow passages 22P has, for example in cross-section a trapezoidal shape and adjacent ones of the first flow passages 22P are separated by an elongate dividing wall 22W that forms along its upper end a first channel. For example, FIG. 5 illustrates twelve of the first flow passages 22P. The first flow passages 22P are smaller than the flat plate segment 17 of the cold-end connecting plate 16 to ensure isolation between the second flow inlet 16A and the second flow outlet 16B as the cold-end rotor 22 rotates relative to the cold-end connecting plate 16. The cold-end rotor 22 has a second channel 22K configured as an annular shape and extending around the periphery of the first flow passages 22P. The cold-end rotor 22 has a third channel 22C configured as an annular shape and extending radially inwardly of the first flow passages 22P. The second channel 22K and third channel 22C are concentric and coaxial with the cold-end rotor 22 and the spindle 25. The first channels each associated with and atop a respective one of the dividing walls 22W, the second channel 22K and the third channel 22C interconnect and communicate with one another and are configured in a hub, spoke and wheel socket configuration complementary to and mating with a hot-end rotor 24 as described further herein. The hub, spoke and wheel socket configuration increases the strength of the hot-end rotor assembly 24 at elevated temperatures (e.g., 2100 degrees Fahrenheit (1149 degrees Celsius)).

As shown in FIG. 5, the cold-end rotor 22 has an upper flange area 22U extending circumferentially around an upper portion of the cold-end rotor 22. The cold-end rotor 22 has a lower flange area 22L extending circumferentially around a lower portion of the cold-end rotor 22. The upper flange area 22U and the lower flange area 22L are separated by a recess 22R. A plurality of vanes 22V extend radially outward and are connected to the upper flange area 22U and the lower flange area 22L.

In one embodiment, the cold-end rotor 22 is manufactured from a plain carbon steel and is adapted to operate at an average temperature of about 450 degrees Fahrenheit (232 degrees Celsius).

As shown in FIG. 1, the rotor 20 includes the hot-end rotor assembly 24 disposed on the cold-end rotor 22 and positioned proximate the hot-end connecting plate 14. The hot-end rotor assembly 24 has a plurality of second flow passages 24P extending therethrough. The hot-end rotor 24 is configured in a hub, spoke and wheel configuration complementary to and mating with the socket configuration of the first channels associated with the dividing walls 22W, the second channel 22K and the third channel 22C.

As illustrated in FIGS. 2 and 3, the hot-end rotor assembly 24 has a hub 24H having an exterior surface 24E with a plurality of first pockets in the form of first axial slots 24K (e.g., rectangular shaped elongate axial oriented recesses) formed therein. The hub 24H has a bore 29 extending therethrough. In one embodiment, the bore 29 has a ceramic fiber blanket 29B disposed therein. The hot-end rotor assembly 24 has an annular rotor rim 26 positioned around and coaxially with the hub 24H. The rotor rim 26 has an interior surface 26N with a corresponding plurality of second pockets in the form of second axial slots 26K formed therein. The rotor rim 26 also defines a generally cylindrical exterior surface 26E.

As illustrated in FIGS. 2 and 3, the hot-end rotor assembly 24 includes a plurality of spokes 28, extending between the hub 24H and the rotor rim 26. Each of the plurality of spokes 28 has a first terminal end 28A and a second terminal end 28B. The first terminal end 28A is seated in one of the first axial slots 24K and the second terminal end 28B is seated in the corresponding one of the second axial slots 26K.

The spokes 28, the rotor rim 26, and/or the hub 24H are manufactured from a ceramic material, such as a ceramic casting. In one embodiment, the spokes 28, the rotor rim 26, and/or the hub 24H are manufactured from a sintered ceramic material.

As illustrated in FIGS. 2, 3 and 11, a ceramic fiber blanket 30 is disposed as packing material at the second terminal end 28B of the spoke 28, in one of the second slots 26K. As shown in FIG. 3, another ceramic fiber blanket 30 is disposed at the first terminal end 28A of the spoke 28, in one of the first slots 24K. The ceramic fiber blankets 30 are adhered to the respective one of the first terminal end 28A and the second terminal end 28B with a sacrificial adhesive to facilitate assembly. This facilitates the spokes 28 being keyed into their respective slots 24K during assembly of the hot-end rotor assembly 24. During operation, the sacrificial adhesive burns off It will be appreciated that, while ceramic fiber blanket is the preferred packing material, any other suitable heat resistant material can be used, for example fibrous matting, felt or woven material.

While the ceramic fiber blanket 30 is shown and described as being between the second terminal end 28B of the spoke 28 in one of the second slots 26K and/or another ceramic fiber blanket 30 is disposed between the first terminal end 28A of the spoke 28 in one of the first slots 24K, the present invention is not limited in this regard as other configurations may be employed including but not limited to the embodiments illustrated in FIGS. 12 and 13. For example, as illustrated in FIG. 12, a channel member 70 (e.g., a metallic or stainless steel channel) is disposed on a respective one or more of the first terminal end 28A and the second terminal end 28B; and the first ceramic fiber blanket 30 is disposed on (e.g., adhered to) the channel member 70. In one embodiment, the relative position of the channel member 70 and the ceramic fiber blanket may be reversed so that the ceramic fiber blanket 30 is disposed on a respective one or more of the first terminal end 28A and the second terminal end 28B and the channel 70 are disposed over the ceramic fiber blanket 30. The channel member 70 increases the strength of the hot-end rotor assembly 24 at elevated temperatures (e.g., 2100 degrees Fahrenheit (1149 degrees Celsius)).

In one embodiment, as illustrated in FIG. 13, a channel member 72 is defined by two segments 72A and 72B, each having an L-shaped cross section and a portion of each of the two segments 72A and 72B overlap each other. A ceramic fiber blanket 30 is positioned over the channel member 72. This embodiment permits the overlapping portions to slide one against the other to accommodate thermal expansion and contraction without applying any substantial circumferential loading to side walls of the respective slots 26K (or 24K) within which they are seated.

As shown in FIGS. 1 and 2, each of the flow passages 24P in the hot-end rotor assembly 24 has a stack of heat transfer plates 32 disposed therein and supported by a rack configuration 51. The heat transfer plates 32 are generally trapezoidal shaped (see FIG. 6) complementarily to the trapezoidal shape of the first flow passages 22P. The heat transfer plates 32 are made from a porous ceramic sponge-like material, such as cordierite, that has a plurality of open pores 32P extending therethrough as shown in FIG. 7.

As illustrated in FIGS. 1, 2 and 9, the rotor rim 26 has an insulation assembly surrounding the exterior surface 26E. The insulation assembly includes a ceramic fiber blanket 40 surrounding and in contact with the exterior surface 26E. As shown in FIGS. 2, 8 and 9, the insulation assembly includes an insulation retaining assembly 44 encapsulating the ceramic fiber blanket 40. The insulation retaining assembly 44 includes a plurality of elongate retainer elements 42. As shown in FIG. 9, each of the retainer elements 42 has a first connection area 42X at one root end 42T thereof (e.g., bottom end, or end adjacent to the cold-end rotor 22); and a second connection area 42Y at the other end (i.e., distal end 42D) thereof (e.g., an upper end or an end adjacent to the hot-end connection plate 14). In one embodiment, the retainer element 42 has an inverted L-shaped configuration defining an elongate first leg 42L (e.g., long leg) and a short second leg 42R (e.g., short leg), with the second leg 42R extending radially inward from the first leg 42L. As shown in FIG. 9, the second connection areas 42Y are positioned on a radially inward end of the second leg 42R. Each of the retainer elements 42 has two first connection areas 42X (as best shown in FIG. 8) and two second connection areas 42Y, as best shown in FIG. 10. As shown in FIG. 10, the second connection areas 42Y of adjacent retainer elements 42 of each group 55 of the retainer elements 42 are connected to one another by a weld 50W. A backing plate (e.g., an arcuate segment 71 of a circumferential length about equal to a length of the group 55 of retainer elements 42) is positioned under the short second leg 42R of the retainer elements 42. A connector plate 50 extends between adjacent ones of the short second leg 42R of the retainer elements 42. The connector plate 50, the short second leg 42R and portions of the backing plate 71 are connected to one another, for example, by the weld 50W. Thus, adjacent ones of second connection areas 42Y of adjacent retainer elements 42 of each group 55 of the retainer elements 42 are restrained from circumferential movement relative to one another.

While the connector plate 50, the short second leg 42R and portions of the backing plate 71 are shown and described as being connected to one another by the welds 50W the present invention is not limited in this regard as the adjacent retainer members 42, the connector plates 50, the short second legs 42R and/or portions of the backing plates 71 may be secured to one another at the second connection areas 42X or other suitable areas by suitable fasteners.

As shown in FIGS. 2 and 8, the insulation retaining assembly 44 includes a plurality of groups 55 of retainer elements 42. Each of the plurality of groups 55 have at least two of the retainer elements 42 connected to one another as described herein. For example, the groups 55 shown in FIG. 2, each have five of the adjacent retainer elements 42 secured to one another at the first connection area 42X and the second connection area 42Y. Collectively, these form a structurally stable arcuate section of bound together retainer elements 42 that can withstand the mechanical effects of thermal expansion and rotation typical during operation of the preheater. While the groups in FIG. 2 are shown and described as having five retainer elements 42, the present invention is not limited in this regard as at least two retainer elements 42 may be employed in each group 55. Alternatively, retainer elements 42 could be constructed from broad sheet material provided with an arcuate cross-sectional profile providing the requisite structural stability at the distal ends 42D thereof.

As shown in FIG. 8, the retainer elements 42 of each of the groups 55 are connected to the upper flange area 22U at the first connection areas 42X, for example by welds 42W joining the first connection areas 42X to the upper flange area 22U, thereby forming a closed loop about a central axis A such that there is no or essentially no circumferential movement of adjacent ones of the first connection areas 42X relative to one another or to the upper flange area 22U. While the retainer elements 42 are described as being connected to the upper flange area 22U at the first connection areas 42X by welds 42W, the present invention is not limited in this regard as the retainer elements 42 may be connected to the upper flange area 22U by other suitable means, such as but not limited to threaded fasteners extending therethrough and threaded into respective threaded bores in the upper flange area 22U.

Adjacent ones of the groups 55 of retainer elements 42 are separate from one another outside of the second connection area 42Y (e.g., are not connected to one another at the second connection areas 42Y) thereby forming a gap 48 between adjacent groups 55 at the second connection areas 42Y. Portions of each (i.e., portions extending away from the first connection areas 42X and away from the root ends 42T, such as the groups 55 of the second connection areas 42Y secured together and the distal ends 42D) of the groups 55 of retainer elements 42 are moveable in a circumferential direction as indicted by the arrows T in FIG. 3, in response to thermal expansion of the rotor rim 26 and/or the ceramic fiber blanket 40, while the arcuate shape of the groups 55 retains the ceramic fiber blanket 40 in a predetermined position (e.g., against the exterior surface 26E). However, each of the second connection areas 42Y, distal ends 42D and the portions extending away from the first connection areas 42X have essentially no radial movement in the direction of the arrow KR in FIG. 9, as a result of thermal expansion and heating of the rotor rim 26 and/or the ceramic fiber blanket 40. The movability of the retainer elements 42 in the circumferential direction prevents the retainer elements 42 from deflecting radially outward and prevents interference of the hot-end rotor assembly 24 with the refractory 12R during rotation of the hot-end rotor assembly 24 at elevated temperatures (e.g., 2100 degrees Fahrenheit (1149 degrees Celsius)).

In one embodiment, the retainer elements 42 are manufactured from a high alloy steel such as but not limited to a type 4562 nitrogen iron nickel chrome molybdenum alloy steel. In one embodiment, the retainer elements 42 are manufactured from the type 4562 nitrogen iron nickel chrome molybdenum alloy steel are welded to the plain carbon steel cold-end rotor 22 via a bi-metallic weld procedure. There is disclosed herein a method for assembling the hot-end rotor 24 to the cold-end rotor 22. The method includes providing the cold-end rotor 22 comprising a plain carbon steel, providing the hot-end rotor 24 comprising a ceramic material, such as a ceramic casting, and providing a plurality of retainer elements 42 comprising a high alloy steel (e.g., type 4562 nitrogen iron nickel chrome molybdenum alloy steel). The method includes wrapping a circumferential exterior surface of the hot-end rotor 24 with the ceramic fiber blanket 40 and positioning a plurality of groups 55 of a plurality of the retainer elements 42 circumferentially around the hot-end rotor 24. The method includes connecting each of the plurality of retainer elements 42 to a circumferential exterior surface of the cold-end rotor 22 (e.g., the upper flange area 22U) via one or more bimetallic welds between and joining the retainer elements 42 to the circumferential exterior surface of the cold-end rotor 22.

Although the present invention has been disclosed and described with reference to certain embodiments thereof, it should be noted that other variations and modifications may be made, and it is intended that the following claims cover the variations and modifications within the true scope of the invention. 

What is claimed is:
 1. An insulation retaining assembly for a high temperature rotary pre-heater having a cold-end rotor and a hot-end rotor, the insulation retaining assembly comprising: a plurality of elongate retainer elements, each of the retainer elements having a root end adapted to be held in fixed relationship to the cold-end rotor and a distal end proximate to the hot-end rotor, portions of each of the plurality of retainer elements being adapted for circumferential movement.
 2. The insulation retaining assembly of claim 1, wherein each of the plurality of retainer elements has a first connection area at the root end and a second connection area at the distal end; a plurality of groups of retainer elements, each of the plurality of groups has at least two of the plurality of retainer elements, adjacent ones of the plurality of retainer elements in each of the groups are secured to one another at the first connection area and the second connection area; and adjacent ones of the groups are secured to one another at the first connection area, thereby forming a closed loop about a central axis and adjacent ones of the groups are separate from one another outside of the first connection area so that each of the groups is moveable in a circumferential direction about the central axis.
 3. The insulation retaining assembly of claim 1, wherein each of the plurality of the retainer elements has an L-shaped configuration defining a first leg and a second leg, the second leg being shorter than the first leg and extending radially inward from the first leg.
 4. The insulation retaining assembly of claim 3, wherein the first connection area is positioned on a first end of the first leg and the second connection area is positioned on a second end of the second leg.
 5. A rotary pre-heater comprising: an annular housing; a hot-end connecting plate having a first inlet and a first outlet, the hot-end connecting plate being secured to a first axial end of the annular housing; a cold-end connecting plate having a second inlet and a second outlet, the cold-end connecting plate being secured to a second axial end of the annular housing; a rotor disposed for rotation in the annular housing and between the hot-end connecting plate and the cold-end connecting plate, the rotor comprising: a cold-end rotor mounted for rotation on a spindle proximate the cold-end connecting plate, the cold-end rotor having a first plurality of flow passages extending therethrough; a hot-end rotor assembly disposed on the cold-end rotor, the hot-end rotor assembly being proximate the hot-end connecting plate, the hot-end rotor assembly having a second plurality of flow passages extending therethrough; an insulation assembly surrounding an exterior surface defined by the annular rim, the insulation assembly comprising a ceramic blanket engaging the exterior surface, and the insulation assembly comprising an insulation retaining assembly engaging the ceramic blanket, the insulation retaining assembly comprising: a plurality of elongate retainer elements, each of the retainer elements having a root end adapted to be held in fixed relationship to the cold-end rotor and a distal end proximate to the hot-end rotor, portions of each of the plurality of retainer elements being adapted for circumferential movement.
 6. The rotary pre-heater of claim 5, wherein each of the plurality of retainer elements, has a first connection area at the root end and a second connection area at the distal end; a plurality of groups of retainer elements, each of the plurality of groups has at least two of the plurality of retainer elements, adjacent ones of the plurality of retainer elements in each of the groups are secured to one another at the first connection area and the second connection area; and adjacent ones of the groups are secured to one another at the first connection area, thereby forming a closed loop about a central axis and adjacent ones of the groups are separate from one another outside of the first connection area so that each of the groups is moveable in a circumferential direction about the central axis. 